Induction devices are used in a variety of electronic components such as transformers, choke coils, inductors, or noise suppression components. Most of the induction devices consist of a core including a soft ferromagnetic material and one or more coils surrounding the core. This induction device is optimized depending on the type to operate at a desired frequency from the direct-current (DC) frequency to the GHz frequency.
In particular, the soft magnetic material is selected as the material of the core, depending on a combination of required characteristics, availability of a material in the form that can be effectively manufactured, and required size/cost necessary to be used in a given market.
In general, preferable soft magnetic materials represent characteristics of high saturation induction, high permeability and low core loss, to minimize size and low saturation coercivity of a core, and the silicon steel sheets, ferrite, amorphous metal, etc., are known as the kinds of the soft magnetic materials.
Specifically, the silicon steel sheet materials are cheap and have a high density, but are limited to have a large core loss in high-frequency use. In addition, since the ferrite has a low saturation flux density, and a poor temperature characteristic, it is not suitable for use of high power components such as high-capacity inverters, coil parts of power sources, and distribution transformers.
Meanwhile, the amorphous metal has a constituent atom having a disordered structure similar to the liquid state, and is manufactured by rapid cooling of molten liquid metal to thus represent various characteristics different from the existing crystalline materials, in particular, show excellent soft magnetic properties.
The amorphous metal is largely classified into iron (Fe)-based metal, cobalt (Co)-based metal, etc., depending on the main ingredient thereof. The Fe-based amorphous metal has a high saturation flux density and a small core loss when compared to those of the silicon steel sheet. Accordingly, the Fe-based amorphous metal is used in a large capacity pole transformer or in a high frequency large magnetic core. The Co-based amorphous metal has a high permeability, and a core loss and coercivity, and thus is used as a high frequency small magnetic core.
Moreover, the amorphous metal has a small core loss and a small eddy current loss when compared to other soft magnetic materials, and thus has been highlighted as the soft magnetic material for magnetic cores on behalf of silicon steel sheets or ferrite. The amorphous metal is excellent in view of high-efficiency, high frequency characteristics due to eddy current losses such as large electrical specific resistivity, noise suppression characteristics by high permeability and high saturation flux density, DC bias characteristics, and responsiveness required for miniaturization.
Products with low core loss characteristics are choke cores, high-frequency transformers for use in inverters, distribution transformers, various reactors, etc. Products using high permeability characteristics are pulse transformers, step-up transformers, audio transformers, current transformers, noise filters, etc. In this case, magnetic cores are classified into a relatively small-capacity gap type toroidal shape core and a relatively large-capacity rectangular shape cut core.
The amorphous metal is supplied as a thin continuous ribbon having a generally uniform ribbon width. However, since the amorphous metal is a very mild material, it is not easy to cut or mold the amorphous metal. If the amorphous metal is annealed to ensure peak magnetic properties, amorphous metal ribbons show noticeably great brittleness. The noticeably great brittleness makes it difficult to use conventional methods and causes costs to rise up to form bulk amorphous magnetic members.
The amorphous metal forming amorphous magnetic cores represents superior magnetic properties to other ferromagnetic materials, but has the difficulty in processing materials due to the above-described physical characteristics. In other words, the manufacturing tools may cause excessive wear at the time of performing a cutting process of forming a gap that gives unique magnetic properties in the conventional amorphous toroidal core or amorphous cut core.
In addition, in the case of the amorphous cut core, the amorphous ribbon is wound and impregnated and then fixed with a glue, to then undergo a cutting process for forming a gap, and a process of polishing a cut surface. This causes a problem of destructing insulation of the cut surface to thus increase the eddy current loss.
Meanwhile, the Korean Patent Laid-open Publication No. 2005-67222 proposed a method of cutting an amorphous metal strip material to form a number of flat thin plates, respectively, to then laminating and aligning the flat thin plates in order to form bulk amorphous metal magnetic components (that is, thin plate laminates) having a three-dimensional shape, and annealing the thin plate laminates in order to improve the magnetic properties, to then bond the thin plate laminates with an adhesive.
The thin plate laminates are formed of only a number of amorphous metal thin plates in the Korean Patent Laid-open Publication No. 2005-67222, and thus gaps and parallel states of the respective thin plate laminates with respect to the adjoining thin plate laminates are adjusted by using a retaining member to thus be mechanically assembled, for example, when the thin plate laminates are joined (or combined) with each other, to thus form a magnetic core (or a magnetic circuit) of a rectangle with a combination of an ‘E-I type, a ‘C-I’ type, or four I types.
Adhesives are used or bands and housings are proposed as the retaining member, in order to prevent a high stress that will result in the degradation of the magnetic properties such as permeability and core loss from being added to the components.
The above-described Korean Patent Laid-open Publication No. 2005-67222 proposed a method of using a lithographic etching process in thin plates of complex shapes and using a stamping process in thin plates of large and simple shapes when cutting amorphous metal strip materials.
However, the lithographic etching process results in an increase in a machining cost to thus make it difficult to be applied to large-scale thin plates. In the case that the complex and large-scale thin plates such as E-, U-, and C-type thin plates employ a stamping machining method, although a punch and a die are configured by using a material having higher hardness than that of the amorphous metal, the wear of the punch and the die is caused in a mass-production process of machining a large number of thin plates, to thereby fail to ensure durability, and result in a rise in machining costs. Thus, a method of sufficiently ensuring the durability of machining equipment is required.
In addition, when the thin plate laminates are joined (or combined) to thus form (or temporarily assemble) a magnetic core (that is, a magnetic circuit) of a rectangle combined with four I shapes, while inserting a spacer in an air gap, and then the magnetic core (or the magnetic circuit) is fixed by a retaining unit such as a band, the two I-type thin plate laminates facing each other are required to be temporarily assembled while maintaining a state parallel to a pre-set interval. However, a structure or method of implementing the required two I-shaped thin plate laminates while maintaining high productivity has not been presented.
Moreover, even if the magnetic core (or the magnetic circuit) such as ‘E-I’ type and ‘C-I’ type is formed (or temporarily assembled) by inserting a spacer into an air gap, a structure of keeping the temporarily assembled state while ensuring a precise air gap similarly to the above-described case is not presented at all.
In addition, when a plurality of thin plate laminates are combined so as to form a magnetic circuit, a mechanical stress is added to the amorphous thin plate laminates, to thus cause a problem of increasing a core loss.